Pressure transducer

Abstract

A pressure transducer having a magnetoresistive element and a magnet displaced with a diaphragm. A magnet supporting device is mounted on an element supporting device both for slidable movement in the displacement-direction of the magnet and for rotatable movement about an axis in the direction, so that the pressure transducer is capable of having a O-point adjustment and a magnetic sensitivity adjustment made independently of each other without interaction between the two when the transducer is assembled.

We claim: 
     
       1. A pressure transducer for sensing the pressure of a gas or liquid and outputting an electric signal in response to the pressure detected comprising: a diaphragm displaceable in response to changes in the external pressure,   a magnet which is displaced with said diaphragm such as to follow the displacement of the diaphragm,   a magnetoresistive element, whose electric resistance is varied in response to changes in the magnetic field, disposed in a position opposed to said magnet,   an element supporting means for supporting said magnetoresistive element,   a magnet supporting means for supporting said magnet mounted on said element supporting means both for slidable movement in the displacement-direction of the magnet and for rotatable movement about an axis in said direction, and   a fixing means for fixing said magnet supporting means and said element supporting means to each other.   
     
     
       2. A pressure transducer according to claim 1, wherein said diaphragm is urged against the external pressure by a spring, and said magnet is supported to said magnet supporting means by means of said spring. 
     
     
       3. A pressure transducer according to claim 1, wherein said magnet supporting means defines a housing of the pressure transducer. 
     
     
       4. A pressure transducer according to claim 1, wherein said element supporting means defines a housing of the pressure transducer. 
     
     
       5. A pressure transducer according to claim 4, wherein said means for supporting the magnet defines a second housing and wherein both said housings are mounted on each other for slidable movement and rotatable movement. 
     
     
       6. A pressure transducer according to claim 5, wherein said fixing means is an adhesive. 
     
     
       7. A pressure transducer according to claim 5, wherein said fixing means is a screw. 
     
     
       8. A pressure transducer according to claim 5, wherein said magnet consists of a pair of permanent magnets oppositely mounted such as to be spaced apart from each other. 
     
     
       9. A pressure transducer according to claim 8, wherein said magnetoresistive element is disposed between said pair of permanent magnets. 
     
     
       10. A pressure transducer for sensing the pressure of a gas or liquid and outputting an electric signal in response to the pressure detected comprising: a diaphragm displaceable in response to changes in the external pressure,   a magnet which is displaced with said diaphragm such as to follow the displacement of the diaphragm,   a magnetoresistive element, whose electric resistance is varied in response to changes in the magnetic field, disposed in a position opposed to said magnet,   an element supporting means for supporting said magnetoresistive element,   a magnet supporting means for supporting said magnet mounted on said element supporting means both for slidable movement in the displacement-direction of the magnet and for rotatable movement about an axis in said direction,   a fixing means for fixing said magnet supporting means and said element supporting means to each other, and   a signal output means for outputting an electric signal corresponding to the electric resistance value of said magnetoresistive element.   
     
     
       11. A pressure transducer according to claim 10, wherein said magnetoresistive element has opposite terminals and an intermediate terminal, and wherein said signal output means includes a voltage applying means adapted to apply the voltage between said opposite terminals of said magnetoresistive element, the potential of said intermediate terminal being output as the electric signal. 
     
     
       12. A pressure transducer according to claim 11, wherein said voltage applying means comprises a second magnetoresistive element having the same temperature characteristic as that of said first magnetoresistive element and connected in parallel therewith, a magnet rigidly secured to said second magnetoresistive element to space said magnet away from said intermediate terminal of said second magnetoresistive element at a distance, and a voltage control means for controlling the voltage of said opposite terminals such as to keep the potential of the intermediate terminal of said second magnetoresistive element constant.